Explaining his decision to leave the group he has led for three-and-a-half years, Hayward said: "I believe this tragedy will leave BP a different company. I believe for it to move on in the United States it needs new leadership and it is for that reason I have stood down as the CEO. I think BP's response to this tragedy has been a model of good social corporate responsibility. It has mounted an unprecedented response."

On CNBC this morning, BP Chairman Carl-Henric Svanberg defended Hayward's tenure, and framed the departure as an opportunity to start anew. Here's Swanberg:

Tony Hayward has done a great job for the company through his almost 30 years...he's driven the company performance and developed the company in many, many ways. He's also lead an unprecedented response in the Gulf of Mexico. But if became obvious to him and us that in order to rebuild our company, in order to rebuild our brand and reputation, we needed fresh leadership and that's why we needed the change.

Svanberg also dismissed a question about whether or not Hayward was a "sacrificial lamb." "That has not all been the discussions. This has been solely a matter of how has been the best leader for the company going forward," he said.